A two-stage surface fatigue crack propagation model of welded joint based on generalized structural stress

Abstract

This work proposes a fracture mechanics model for fatigue crack propagation on the surface of welded structures using generalized structural stress. The model considers the impact of the weld profile on structural stress parameters. The whole process of crack propagation on the surface of welded joints is divided into two phases: shallow surface (a/t ≤ 0.2) and long crack (a/t > 0.2). The geometric modification coefficient F of fracture mechanics for different geometrical features of welded structures in tensile and bending load modes were calculated by multiple regression. The total thickness amplification factor M_kn is used to quantify the influence of the notch effect on the stress intensity factor (SIF) of shallow surface cracks. A unified fracture mechanics model explains the two stages of solving the dynamic SIF and the remaining life for surface cracks in welded joints. The results show that the model enhances the calculation accuracy of the SIF for welded joints, which is valuable for assessing the structural integrity and safety of welded joints.